Testing apparatus



G. W. PICKARD TESTING APPARATUfi Filed 4111-11 25, mo

Sept. 29, 1925. 1,555,249

Fig.3.

Patented Sept. 29, 1925.

UNITED STATES V 1,555,249 PATENT OFFICE. I

GRERNLEAF WHITTIER PICKARD, OF NEWTON, MASSACHUSETTS, ASSIGNOR TOWIRELESS SPECIALTY APPARATUS COMPANY, OF BOSTON, MASSACHUSETTS, A

CORPORATION OF NEW YORK.

.rnsrme APPARATUS.

I Application filed April 23, 1920. Serial No. 376,132.

To all whom it may concern:

Be it known that I, GREENLEAF W. PICK- ARD, a citizen of the UnitedStates, residing at Newton, in the county of Middlesex and State ofMassachusetts, have invented cer tain Improvements in Testing Apparatus,of which the following description, in connection with the accompanyingdrawings, is a specification, like'reference characters on the drawingsindicating like parts in the several figures.

This invention relates to distinguishing bad from good sheets of mica orother dielectric or insulating materials. The invention will be hereindisclosed as embodied in apparatus designed particularly for testingdielectric elements to be used in electrical condensers. These elementsare subjected to the distinguishing operation before being assembled inthe condenser so that the. de fective elements can be eliminated. It canthus be definitely determined before the assembling operation is begunthat only perfoot dielectric elements shall go into the con-- structionof'the'condensenand the expense and annoyance which otherwise would becaused by the presence of defective elements thus is eliminated.

The present invention has for its chief object to devise an apparatuswith which such distinguishing method can be performed veryaccuratelyand'rapidlyand which will require a minimum of skill and care on thepart of the operator. It is a further important object of this inventionto devise an apparatus of this character which, in addition toperforming and testing operation, will also automatically separate thedielectric electrically distinguishing operation, also will separate thedefective dielectric sheets or films from the good ones by meanscontrolled by-the presence of defects inthe bad sheets. n

I The nature of the invention will -be'readily understood from thefollowing. description and the novel features will be particularlypointed out in the appended claims.

Referring now to the accompanying drawings, v

Figure 1 is a diagrammatic .view of an apparatus embodying the presentinv ntlon;

the apparatus and Fig. 3 is a plan view of a sheet of mica to be tested.

Preliminary to a detailed description of the apparatus it should bestated that the entire surface of a mica sheet, or other dielectricelement of a condenser, is not sub jected to a dielectric strain whilein use. That is, the conducting elements are smaller than the'dielectricelements so that a margin is left around the entire edge of eachdielectric element which is substantially free from the dielectricstrain, this margin serving primarily to prevent the current fromjumping around the edge of the mica sheet between the two adjacentconducting elements separated by said sheet.

In Fig. 3 M indicatesamica sheet and m the active area of the sheet;that is, the area subjected'to the dielectric strain. It is this area mwhich must be tested but it is not necessary to test the dielectricstrength of the inactive margin, and in the present machine it iscontemplated that this margin will not be tested.

The apparatus shown comprises two metal rolls 2 and 3, respectively,mounted one above the other, and rotatin on metal shafts which aresupported in ame pieces 44 made of insulatin material. Thus the rollsare electrically insulated from each other at all places except at theirperipheries. The rolls may be driven from any, suitable source of motivepower and they are connected together by gears 5 and 6 made ofinsulating material such as bakelite, fibre, or the like. They arerotated in the directions indicated by the arrows in Fig. 1 and the micasheets are fed between the rolls one at a time.

Each roll is of a length equal to one dimension of the area m so thatwhen the sheets are run through them the opposite margins of each sheetproject beyond the .ends of the rolls so that there will not be such adischarge from one roll to the other over the edges of the sheet testedas to prevent the proper testing of the sheet.

-These two rolls are connected in a high potential circuit comprisingthe secondary 7 of an induction coil or transformer, one terminal ofthis secondary being connected by a conductor 8 to the roll 2 While theother terminal is connected by a conductor '9 (hrough'the primary 10 ofanother induction coil to the lower roll 3. .For convenience in makingthese-connections, the ends of the shafts on which the rolls are mountedare extended through one of'the supports 4,

as indicated at the left of Fig. 2, and spring switches designated at 17and 18, respective-- l The switch 17 comprises a ivotedconcfilcting arm19 carring a r0120 at its upper end and norma ly held by a spring 21against the end ofa stop screw 22 and a spring mounted contact 17 withwhich arm 19 engages to close thecircuit: The other switch 18 is likethe switch 17 and includes a pivoted conducting .arm 23 carrying a roll24 at its upper end and normally held open by a spring 21. This primacircuit, therefore, is normally open. It Wlll be seen from an inspectionof Fig. 2 that the rolls 20 and 24 are mounted closely adjacent to theopposite ends of the rolls 2 and 3 and that the upper edges of the rolls20 and 24 lie just above the level of the line of con tact of the rolls2 and 3. The distance from the line of contact of the rolls 2 and 3 withthe mica sheet to the top of each roll 20 and 24 is equal to the widthof the inactive margin of the mica sheets shown at m, Fig. 3. Normallyboth the primary and secon ary circuits are inactive since the switches17 and 18 are open. When, however, a sheet of mica is fed between therolls 2 and 3, the forward or leading edge of the mica sheet firstengages the roll 20 and depresses it, thus closing the switch 17. Whenthis edge of the sheet emerges from between the rolls a distance equalto the width of the margin m, Fig. 3, the roll 24- will then be movedfar enough by its engagement WlthzSflld sheet to close the switch 18. Atthis instant, therefore, the primary circuit is closed and theinterrupted current flowing therethroughcreates a high potential in thesecondary circuit which potential is impressed across the sheet of micabetween the rolls. That is, the rolls form, in effect, terminals for thehigh potential circuit. Asthe sheet is advanced by the rolls, all partsof its active area m are subjected to the potential created in thesecondary circuit. But as soon as the rear or trailing edge of the sheetlgaves the roll 20, the spring 21 opens the switch 17 and thusinterrupts the action of the primary, and consequently, also, thesecondary circuit. The switch 18 is opened an instant later by itsspring when the mica moves out of contact with it. It will beunderstood, of course, that the springs that operate the arms'19 and 23are very light.

If the mica has no fault or flaw which will permit the applied potentialto drive a current through the flaw, no current will flow in thesecondary circuit. If, however, the sheet has a hole in it,"or for anyother reason breaks down at a fault or flaw, then a current will flowthroughthe" secondary circuit. This current energizes the primary coil10 which induces a current in the secondary 27 of'a low potentialcircuit that also includes a relay coil 28. The energizing of this coillifts an armature 29 thus closing a switch 30 and causin a flow ofcurrent from a battery 31 throug a's'olenoid 32.. This solenoid attractsan armature 33 on the depending end of a plate 34 which is vpivoted at35 and normally rests against astop screw 36. Y

It will be seen that the plate 34 forms normally a continuation of aninclined apron or chute 37dow-n which. the mica sheets slide as they areejected from between the rolls 2 and 3. If the plate 34 is in itsnormalposition, these mica sheets will slide into the forward part of areceptacle 38, but if the plate 34 is tipped into its dotted lineposition as shown in Fig. 1', the mica sheet then will drop into thereaward part of this. receptacle. A' partition, not shown, separates thefront and rear portions of the receptacle. It will thus be seen that theplate 34 is operated automatically to'separate the perfect from theimperfect sheets of mica;

the perfect sheets sliding into the forward part of the receptacle 38and the defective sheets into the rearward part. That is, the plate 34acts as an automatic switch or deflector to direct the perfect andimperfect sheet-s into different paths.

In case a sheet of mica under test contains a small hole or other flawnear its forward edge while the remainder of the sheet is perfect, thereis danger that the switch or deflector plate 34 after being swung intoits dotted line position will drop back again before the imperfect sheetis delivered due to the fact that the flow of current through thesecondary circuit will be cut off at a relatively early point'in thetesting of that sheet. In such an event the defective sheet -'of micawould be delivered to the forward part of the receptacle 38 with theperfect sheets. In order to prevent this action the core of coil 28 thatoperates the armature 29 is provided with a locking winding 40 which isin circuit with a switch 41tl1at is closed when the relay 28 isenergized and is also in circuit with a battery 42 and another switchcomprising the pivoted arm 19 and the stop screw 22. The latter switchis in arallel with a switch 43 in circuit with windmg 40 and normallyheld open by a spring 44 but arranged to be closed by a solenoid 45 inseries with the switches 17 and 18 and with the battery 14.

This parallel arrangement of switches ensures that after the switch arm29 has once been lifted it will be held in its raised position due tothe action of the locking winding 40 as long as either switch 43 orswitch 19, 22, is closed, the two Switches operating alternately. Thatis, if the coil 28 has been because the parts 19 and 22 will, by thattime, have come into engagement and will still keep this circuitclosed.When, however, a new mica film is fed into the machine the depression ofthe roll 20 will break the contact between the parts 19 and 22 and thelocking circuitthen will be opened, allowing the armature 29 to dropinto its lower position, thus opening the switches 30 and 41 andreleasingthe deflector plate 34 which will fall back against its stop36.

To prevent the opening of the locking circuit upon the breaking of thecircuit of coil 45 and the opening of. switch 43, a leaf spring 46is'attached at oneend to member 19, and is free at its. opposite end toyieldingly engage and disengage contact 22.

When roll 20 is depressed, member 19 moves downwardly and engagescontact 17 a and slightly depresses it by reason of its spring mounting.By this time, spring 46 has disengaged contact 22.

lowing in engagement therewith until spring 46 again engages contact 22.Thereafter member 19 and contact 17 separate by reason of the continuedmovement of member 19, this continued movement being allowed by spring46. The switches 17 and 18 are so arranged that the potential is appliedwhile the sheet is held between the rolls and the potential is releasedbefore the sheet is released, thus preventing discharges be- "ltween theterminals which tend to heat the mica, causing it to deteriorate. It isto be understood that other apparatus for performing this method ofapplying and releasing potential only while the sheet is pressed betweenterminals may be used.

It' will now be evident that this invention provides a very simpleapparatus with the aid of which mica sheets or films can be tested veryrapidly; and that the machine, in addition to testing the sheets, willautomatically separate the sheets that are defective from thegood'sheets. The voltage impressed across the rolls 2 and 3 can beadjusted as desired by using a suitable type of transformer or inductioncoil, so that the same apparatus at different times can be While thedielectric material to has been referred toabove and also in the Whenroll 20 is re leased, member 19raises, the contact 17 fol-' used fordifferent lots of micas of different thicknesses.

While I have herein shown and described the best embodiment of theinvention of which Iam at present aware, it will readily be appreciatedthat this embodiment may be modified in many particulars withoutdeparting from the spirit or scope of this invention.

be tested appended claims as mica, it will be understood that otherdielectrics are the equivalent of mica so far as the present inventionis concerned.

What is claimed as new. is:

1. An automaticmica-sheet flaw-detecting and selecting machine, whichcomp-rises two electrically conducting members constituting circuitterminals having sufficiently wide continuous conducting surface areasto engage continuously substantial widths of the opposite surfaces of anintervening.

mica sheet; .means causing an electric current to flow through a flaw ina defective intervening mica which does not cause a current to flowthrough a good intervening mica; mechanism moving successive micas topositions between and ejecting them from between said conductingmembers; and

mechanism controlled by such current flow through defective micas andsegregating the good and the-bad ejected micas.

2. An automatic mica-sheet flaw-detecting. machine comprising, incombination, a

pair of electrically conducting rolls mounted to be adjacent to oneanother for simultaneously engaging opposite portions of the twosurfaces of a.mica sheet, means for driving said rolls to cause them tofeed said sheet therethrough, and a high potential circuit in which saidrolls are connected and for which they form terminals, whereby a flow ofcurrent in said circuit is normally prevented by the presence of goodportions of said mica sheet-between the rollsbut is permitted when adefective part of the sheet passes between said rolls.

3. An automatic mica-sheet flaw-detecting machine comprising incombination a pair of electrically conducting rolls mounted to beadjacent to one another for simultaneously engaging opposite portions ofthe two surfaces of a mica sheet, means for driving said rolls to causethem to feed said sheet therethrough, and a high potential circuit inwhich said rolls are connected and for which they form terminals, andcontrolling means for said circuit arranged to be operated by theforward edge of the mica sheet as the rolls draw the sheet betweenitself controlled by said moving mechanism;

and mechanism controlled by the current flow through defective micas andsegregating the good from the bad ejected micas.

5. An automatic mica-sheet flaw-detecting and selecting machine, whichcomprises two electrically conducting members constituting circuitterminals having sufliciently wide continuous conducting surface areasto engage continuously substantial Widths of the opposite surfaces of anintervening mica sheet; means causing an electric current to flowthrough a flaw in a defective intervening mica which does not cause acurrent to flow through a good intervening mica; mechanism for movingsuccessive micas to positions between and ejecting them from be- 0 tweensaid conducting. members; at least one of said terminals having a widthless than the mica sheet whereby the sheet in testing position extendsto a limited degree beyond said terminal; controlling means for saidcurrent-causing means and itself controlled by said moving mechanism;and mechanism controlled by said current floor through defective micasand segregating the good from the bad ejected micas 6. A mica testingmachine comprising, in combination, a pair of rolls for simultaneouslyengaging opposite faces of a mica sheet, means for driving said rolls-tocause ,them to feed said sheet therethrough, and a high potentialcircuit in which said rolls are connected and for which they formterminals, a device movable into either one of two operative positionsfor controlling the path taken by the ejected mica sheets, and automaticmeans for shifting said device from one of said positions to the otherto direct the perfect and imperfect sheets into different paths upontheir discharge from be tween said rolls and for automatically holdingsaid device in its shifted position until after the sheet for which itis shifted has passed said device.

- 7. An automatic mica-sheet flaw-detecting machine comprising, incombination, a pair of electrically conducting rolls mounted to beadjacent to one another for simultaneously engaging opposite portions ofth two surfaces of a mica sheet, means for driving said rolls to causethem to feed said sheet therethrough, means for impressing a high twan-a potential across said rolls whereby a mica sheet fed between themwill be subjected to a dielectric strain, a deflector normally held inposition to direct the sheets ejected from between said rolls in apredetermined path, and means acting automatically upon the passagebetween the rolls of a dielectrically weak portion of the micasheet, toshift said deflector into a position causing the defective sheet tofollow a different path.

-8. A mica testing machine comprising, in combination, a pair of rollsfor simultane ously engaging opposite faces of' a mica sheet, means fordriving said rolls to cause them to feed said sheet therethrough, and ahigh potential circuit in which said rolls are connected and for whichthey form ter minals, whereby a flow of current in said circuit isnormally prevented by the presence of said mica sheet between the rollsbut is permitted when a defective. part of the sheet passes between saidrolls, a deflector normally held in'a position to direct the sheetsejected from between said rolls in a predetermined path,electro-magnetic means operative automatically upon a .flow of currentthrough said circuit permitted by the passage of a defective sheet toshift said deflector into a position causing the ejected sheet to followa different path, and means operative to ensure the retention of saidde- Hector in its shifted position until said defective sheet has beendirected into the desired path.

9. An automatically operating mica-sheet flaw detecting and selectingmachine comprising, in combination, a pair of electrically conductingrolls mounted to be adjacent to one another for simultaneously engagingopposite portions of the surfaces of a mica sheet, means for drivingsaid rolls to cause them to feed said sheet therethrough, and a highpotential circuit in which said rolls are connected and for which theyform terminals, whereby a flow of current in said circuit is normallyprevented by the presence of said mica sh wt between the rolls but ispermitted when a defective part of the sheet passes between said rolls,a deflector nor mally held in a position to direct the sheets ejectedfrom between said rolls in a predetermined path, electro-magnetic meansfor shifting said deflector into a difl'erent position, and a relaycontrolling the operation of said electro-magnetic means and arranged tobe energized by a flow of current through said high potential circuit. i

10. A mica testing machine comprising, in combination, a pair of rollsfor simultaneously engaging opposite faces of a mica sheet, means fordriving said rolls to cause them to feed said sheet therethrough, and ahigh potential circuit in which said rolls are connected and for whichthey form terminals, whereby a flow of current in said circuit isnormally prevented by the presence of said mica sheet between the rollsbut is permitted when a defective part of the sheet passes between saidrolls, a deflector normally held in a position to direct the sheetsejected from between said rolls in a predetermined path,electro-magnetic means for shifting said deflector into a differentposition, a relay controlling the operation of said electro-magneticmeans and arranged to be energized by a flow of current through saidhigh potential circuit, and a locking circuit for maintaining saidelectro-nragnetic means energized after its operation has been initiateduntil after the testing operation on the sheet which permitted the flowof current through said circuit has been completed.

11. A mica testing machine comprising, in combination, a pair of rollsfor simultane;

ously engaging oppositevfaces of a mica sheet, means for driving saidrolls to cause them to feed said sheet therethrough,, a high potentialcircuit in which 'said rolls are connected and for which they formterminals, whereby a flow of current in said circuit is normallyprevented by the presence of said mica sheet between the rolls but ispermitted when a defective part of the sheet passes between said rolls,a deflector normally held in-a position to direct the sheets sheet,means ejected from between said rolls in a predetermined path,electro-ma'gnetic means operative automatically upon a flow of currentthrough said circuit permitted by the passage of a defective sheet toshift said defiector into a position causing the ejected sheet to followa different path, and a looking circuit for said electro-magnetic meansloperative to ensure the retention of said deflector'in its shiftedposition until said defective sheet has been sired path, said lockingcircuit includinga switch arranged to be operated by thepresentationofthe next sheet of mica to said rolls to open said locking circuit andthereby enable said deflector to return to its original position.

12. An automatically operating mica- .sheetfiaw-detecting and selectingmachine,

which comprises a pair ofelectrically conducting members constitutingcircuit terminals having sufficiently wide continuous connism controlledby said current flow through d between two circuit terminals having-wideducting surfaces to engage continuously substantial widths of theopposite surfaces of the mica-sheet; means causing anelectric current toHow through a flaw in adefective mica between said conducting memberswhich does not cause a' current to flow through a good mica so located;means for ejecting. the 1micas successively from between said conductingmembers ;'and mechadefective micas and segregating the goo and thebadejected micas.

13. A testing apparatus comprising, in

directed into the de-.

combination, two electrically conducting members mounted to engagesimultaneously opposite faces of a sheet of mica, a high potentialcircuitconnected to said members and for which the members formterminals, a primary circuit supplying powerto said high potentialcircuit, and controlling means for said primary circuit normally,holding the latter circuit open but mounted and arranged to be .operatedto close said circuit upon the presentation of a mica sheet in testingposition.

l4. A ,m1ca testing machine comprising, in combination, a pair of rollsfor simultaneously engaging opposite faces of a mica sheet, means'fordriving said rolls to cause them to feed said sheet therethrough, and ahigh potential circuit in which said rolls are connected and for whichthey form terminals, switch operating elements controlling said circuitand maintaining it normally inactive but mounted and arranged to beengaged by both the leading and trailing edges of saidmica sheet wherebysaidcircuit is inactive whenever either one of sai elements is notengaged bya mica sheet.

15. A mica testing machine comprising, in combination, a pair of rollsfor simul taneously engaging opposite faces of a mica for driving saidrolls to cause them to feed said sheet therethrough, a high potentialcircuit in which said rolls are connected and for which they formterminals, and two normally open switches connected in series andcontrolling said circuit, said switches having operating elementsmounted, respectively, one in front of and the other behind the line ofcontact of said rolls with the mica sheet whereby both of said elementsare engaged by the sheet as it is fed through the rolls;

16. A mica testing machine comprising, in combination, a pair of rollsfor simultaneously engaging opposite faces of a mica sheet, means fordriving said rolls to cause them to feed said sheet therethrough, ahighpotential circuit in which said rolls are mounted and for which theyform terminals, a primary circuit supplying'power to saidhigh potentialcircuit, and two switches connected in said primary circuit-in serieswith each other,omeans for normally holding said switches open, anoperating element for each of said switches, said elements being locatedone in front of and the other behind the line of contact of said rollswith the mica sheet whereby they are operated to close the switches bytheir contact with said sheet.

17. The method of applying a flaw-detecting difference. of electricalpotential to the opposite surfaces of a dielectric sheetcontinuousconducting surfaces continuously engaging substantial widths of theopposite surfaces of the sheet, which consists, after locatmg the sheetbetween the terminals, in

I successively pressing the terminals into firm engagement with thesheet and relieving the sheet from such terminal-compression, causingsuch pressing and release of the sheet to effect the application and thediscontinuance respectively of the flaw-detecting potential to theterminals.

18. Apparatus for distinguishing good mica sheets from similar sheetspossessing minute defects not readily observable,,comprising a pair ofelectrically conducting members having sufiiciently wide continuoussurfaces to engage continuously substantial widths of opposite micafaces; m"chanism moving successive micas to positions between saidconducting members; and means controlled by said moving mechanism andoperating while a mica is between said conducting members, and causingthe application of such a potential difference to said conductingmembers as will cause a current to flow through a defect in a defectivemica but not through a good mica.

19. An automatically operating machine for detecting flaws in dielectricsheets which comprisis a pair'of electrically con ducting membersconstituting circuit terminals having sufficiently wide continuousconducting surface areas to engage continuously substantial widths ofthe sheet; means for moving the sheets to positions between and ejectingthem from between said terminals; means controlled by the sheet in itsmovement and connecting the terminals in their circuit; means associatedwith.

said circuit for causing the application of such potential difference tosaid terminals as will causea current to flow through a defect in adefective mica but not through a good mica; and means automaticallyreturning said connecting means to its normal disconnecting positionupon further movement of said sheet but prior to the ejection thereof.

20. An automatically operating micasheet flaw-detecting machine, whichcomprises a pair of sheet-feeding rolls mounted to e normally inperipheral contact with one another; means for rotating the rolls tofeed the mica sheet between them; and means for subjecting the micasheet to a high electric stress while it is being fed by said rolls.

21. An automatically operating micasheet flaw-detecting machine, whichcomprisesa pair of sheet-feeding rolls mounted to be normally inperipheral contact with one another; means for rotating the rolls tofeed the mica sheet between them; insulating supports for the ends ofsaid rolls and between which the sheet passes while being fed betweenthe rolls; and means for subjecting the mica sheet .to a high electricstress while it is beingifed by said rolls.

22..An automatically operating machine for detecting flaws in a micasheet, which comprises two conducting members constituting circuitterminals having sufiiciently wide and continuous conducting surfaces toengage continuously a substantial portion of the width of the sheet; andin ans, operated by movement of said sheet and only when the sheet is insuch engagement with .both terminals, to appl and remove, suc-'cessively, a difl':rence 0 electrical potential between said terminalsand the opposite surfaces of the sheet.

23. An automatically operating micasheet, flaw-detecting machine, whichcomprises rotatable sheet-feeding vmeans; and means, operating while thesheet is being fed by said means, causing an electric current to flowthrough a flaw in a defective mica sheet which does not cause a currentto flow through a good mica sheet.

24. Apparatus for distinguishing and segregating good mica sheets andsimilar sheets possessing minute defects not otherwise observable, saidapparatus comprising two electrically conducting members haw ingsufiiciently wide continuous surfaces to engage continuously substantialwidths of opposite mica faces; mechanism moving successive micas'topositions between and e ecting th'm from between sald conduct-.

ing members; means controlled by said moving means and operated when amica is engaged by and between said conducting members and applying sucha potential difference to said conducting members as will cause acurrent to flow through a defective mica "but not through a good mica;and mechanism' controlled by such current flow through defective micasand segregating the good and the bad ejected micas.

'25. Apparatus for distinguishing good mica sh'ets from similar micaspossessing minute defects not readily observable, said apparatuscomprising two members having relatively movable electrically conductingmica-engaging surfaces; mechanism moving a mica-engaging surface of atleast one of said conducti members toward the other into position toengage a mica between them;- means applying to said conducting surfacessuch an electrical potential difference as to cause a flowofcurrent-through a defect in a defective mica but not through a goodmica; a switch controlling said poten'tial applying means; and mechanismcontrolled by continued operation of said conducting member moving meanswhile the mica is engag'd by said conducting surfaces, and operatingsaid switch to cause operation of said means for applying potentialdifierence. Y

In testimony whereof I have name to this specification.

' GREENLEAF WHITTIER PICKARD.

signed my

